By CATHY ARONSON
HAMILTON - Mighty River Power wants lower minimum and higher maximum levels of the Waikato River's hydro lakes as part of its proposed 35-year resource consent application.
The generation company claims greater flexibility of lake levels would help it supply peak demand by hydro-generation in a cheaper and more environmentally friendly way.
Chief executive Doug Heffernan said it could store more water for peak demand and plan the hydro system flows to provide water according to demand.
Eighty per cent of the time the lake levels would be normal and would change only during unusual demand.
There would be a noticeable change in lake limits at Atiamuri, Maraetai, Waipapa and Karapiro.
Atiamuri's minimum level would be nearly two metres lower to allow it to cope with increased water to flow downstream to Whakamuru and Maraetai during peak demand.
Lake Karapiro's maximum level would be increased by almost a metre but its minimum level would change by only 0.02m.
Lake Karapiro is the most-used hydro lake for recreation but Mighty River Power claims the increased level would not inhibit access to the river and would reduce weed nuisance.
Environment Waikato chief executive Barry Harris said the effect of lake levels on recreation would be one of the biggest issues in the resource consent.
If the levels were too high, it would be difficult to gain access to them and the risk of flooding increased.
If they were too low, access would again be difficult and erosion become a problem.
He said flood management, impact of additional flows on low-lying areas and the effect on plant and animal life would be issues.
Mr Harris said the resource consent under the Resource Management Act had a greater weight on environmental and community concerns than the present permits governing Mighty River Power's operation, which expire next October.
"There will have to be a tradeoff between the ranges that are the most effective for Mighty River Power's operation and levels that are acceptable to the community who use them."
River levels have already caused community uproar this year. Mighty River Power planned to lower the flow of the Waikato River over summer to ensure there was enough water for generation if Lake Taupo's level fell too far.
The plans were opposed by the Hamilton City Council, which said its sewage plant would not have enough water and would have to use the costly city water supply.
The council also said the low levels could damage a Hamilton bridge if the timber piles were exposed to the air.
City councillor Dave Macpherson said jetties and boat ramps would be out of the water.
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